Process for treatment of aqueous effluent

Abstract

The invention relates to the treatment of mine tailings in the form aqueous effluents comprising solid particles. With the process of the invention it is possible to separate all or part of the water from an aqueous effluent comprising solid particles. This process comprises (a) adding to the effluent at least one anionic modified natural polymer selected from among anionic guar gums and/or anionic starches, then (b) adding at least one cationic modified natural polymer selected from among cationic starches and/or cationic dextrans and/or cationic chitosans.The invention also relates to a composition comprising an aqueous effluent comprising solid particles treated with an anionic modified natural polymer and a cationic modified natural polymer. Preferably, it concerns a composition comprising an aqueous effluent comprising solid particles, at least one anionic modified natural polymer selected from among anionic guar gums and/or anionic starches, and at least one cationic modified natural polymer selected from among cationic starches and/or cationic dextrans and/or cationic chitosans.

The invention claimed is: 
     
       1. A process for treating an aqueous effluent comprising solid particles, said process comprising:
 (a) adding at least one anionic modified natural polymer to the effluent, wherein said anionic modified natural polymer is anionic guar gum, and 
 (b) adding at least one cationic modified natural polymer selected from the group consisting of cationic starch and cationic dextran, 
 wherein the effluent is selected from the group consisting of:
 effluent from the mining extraction of coal mines, diamond mines, phosphate mines, metal mines; 
 effluent from the mining extraction of bituminous sand or oil sand; 
 effluent comprising 5 to 70% by weight of solid particles; 
 effluent comprising sand, clay and water; 
 effluent comprising sand, clay, water and residual bitumen; 
 effluent comprising fresh tailings; and 
 effluent comprising fine tailings; 
 
 wherein the anionic modified natural polymer has a degree of substitution of between 0.01 and 3; and 
 wherein the cationic modified natural polymer has a degree of substitution of between 0.1 and 3. 
 
     
     
       2. The process according to  claim 1 , wherein the anionic modified natural polymer is added in an amount by weight ranging from 10 to 10 000 ppm relative to the quantity of solid particles contained in the aqueous effluent. 
     
     
       3. The process according to  claim 1 , wherein the anionic modified natural polymer has a molecular weight ranging from 3 to 50 million g/mol. 
     
     
       4. The process according to  claim 1 , wherein the anionic modified natural polymer has a charge density of between 0.1 and 15 meq/g. 
     
     
       5. The process according to  claim 1 , wherein the cationic modified natural polymer is a cationic starch. 
     
     
       6. The process according to  claim 1 , wherein the cationic modified natural polymer is added in an amount by weight ranging from 50 to 1 000 ppm relative to the quantity of solid particles contained in the aqueous effluent. 
     
     
       7. The process according to  claim 1 , wherein the cationic modified natural polymer has a molecular weight ranging from 100 000 to 50 million g/mol. 
     
     
       8. The process according to  claim 1 , wherein the cationic modified natural polymer has a charge density of between 0.5 and 10 meq/g. 
     
     
       9. The process according to  claim 1 , wherein the weight ratio between the anionic modified natural polymer and the cationic modified natural polymer is between 15:1 and 5:1. 
     
     
       10. The process according to  claim 1 , also comprising the separation of all or part of the water from the mixture of solid particles treated with an anionic modified natural polymer and a cationic modified natural polymer. 
     
     
       11. The process according to  claim 10 , wherein at least 20% by weight of water is separated. 
     
     
       12. The process according to  claim 1 , wherein the fine tailings in the effluent are selected from the group consisting of:
 fresh fine tailings (FFTs); and 
 mature fine tailings (MFTs). 
 
     
     
       13. The process according to  claim 1 , wherein the metal mines are selected from the group consisting of aluminium mines, platinum mines, iron mines, gold mines, copper mines, and silver mines. 
     
     
       14. A method of treating solid particles contained in an aqueous effluent comprising adding to said aqueous effluent at least one anionic modified natural polymer comprising anionic guar gum, and at least one cationic modified natural polysaccharide selected from the group consisting of cationic starches and cationic dextrans,
 wherein the anionic modified natural polymer has a degree of substitution of between 0.01 and 3; and 
 wherein the cationic modified natural polysaccharide has a degree of substitution of between 0.1 and 3. 
 
     
     
       15. A composition comprising an aqueous effluent comprising solid particles, at least one anionic modified natural polymer comprising anionic guar gum and at least one cationic polymer selected from the group consisting of cationic starches and cationic dextrans,
 wherein said effluent is selected from the group consisting of:
 effluent from the mining extraction of coal mines, diamond mines, phosphate mines, or metal mines; 
 effluent from the mining extraction of bituminous sand or oil sand; 
 effluent comprising 5 to 70% by weight of solid particles; 
 effluent comprising sand, clay and water; 
 effluent comprising sand, clay, water and residual bitumen; 
 effluent comprising fresh tailings; and 
 effluent comprising fine tailings; 
 
 wherein the anionic modified natural polymer has a degree of substitution of between 0.01 and 3; and 
 wherein the cationic modified natural polymer has a degree of substitution of between 0.1 and 3. 
 
     
     
       16. The process according to  claim 15 , wherein the metal mines are selected from the group consisting of aluminium mines, platinum mines, iron mines, gold mines, copper mines, and silver mines.